Question 351137
Hello, 
Well, this seems a bit advanced for a 4th grader. 
First we'll let x show one side and 1/2x+20 for the other side. 
Now we can set up an equation:
x(1/2x+20)=4800
Expand this out to:
1/2x^2+20x=4800
Subtract 4800 from both sides to get:
1/2x^2+20x-4800=0
Multiply by 2 to get rid of the fraction:
x^2+40x-9600=0
This can be factored as:
(x-80)(x+120)=0
solve for x to get:
x=80
x=-120
80 is the sensible answer, so the sides are
80 cm and 60 cm
This can be checked by multiplying these to get 4800 sq cm
Got it?
RJ
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